In parts of Europe celiac disease is considered one of the most common chronic autoimmune diseases. It has been identified as a cause of significant morbidity and an increased risk of malignancies. Celiac disease is thought to be quite rare in the United States. Because it is thought to be rare, it is rarely considered in the differential diagnosis of many common conditions. As general population screening requires a great expenditure of resources it would make sense to study the prevalence of the disease in those groups of people most likely to have it. If it is present in these groups at the same level as has been seen in countries where celiac disease is common then this would justify consideration of more widespread screening. This study aims to examine the prevalence of celiac disease in those thought most at risk: Type one diabetes, family history of celiac disease or dermatitis herpetiformis; osteoporosis, chronic diarrhea with abdominal pain, and iron deficiency anemia (Specific aim number 1). We will use standardized validated gastrointestinal questionnaires to identify any clinical predictors of the who may have celiac disease (Specific aim number 2). We aim to study whether the HLA associations seen in European populations are unaltered by the more heterogenous population of the US and screen for other predictive HLA genotypes for disease risk in American celiacs (Specific aim number 3). If celiac disease is a common condition, that is undiagnosed, it is important to know what benefit (or detriment) may accrue to the individual when the diagnosis has been made. To study how making the diagnosis of CD as the result of a screening project affects both gastrointestinal and non- gastrointestinal symptoms, the patient's quality of life, and the utilization of health care resources (Specific aim number 4). If this proposal demonstrates that celiac disease is more common than believed, it will provide important insights into who it affects, how to detect the condition or predict risk, while demonstrating a substantial benefit in both relief of suffering, improved functioning and reduced utilization of health care. This will be possible, because the subjects who will be diagnosed with CD will actually live in Olmsted County, and their medical histories and ongoing medical care will be recorded in community medical records accumulated by the Rochester Epidemiology Project.